briancollins
Octane Boostaholics
This might be an awful stupid question but is it possible to fit a waste gate instead of a dump valve? I just prefer the sound of the wg's!
Dump Valve or Waste Gate
- Thread starter briancollins
- Start date
briancollins
Octane Boostaholics
well i assume ya know the sound of a dump valve?! impossible to describe the sound of a WG. Just sounds far nicer in my opinion anyway.
keith dublin
Member Number 161Full ISDC Members 2015
It sounds like a kind of a chatter noise if you get me 
briancollins
Octane Boostaholics
that is probably the best way to describe it!
E
ericsti
Guest
Just to see! Does the Waste Gate sound anything like a snake Hissing?
S
six spoke clive
Guest
:lol: :lol: :lol:
ring ttm
they can do them all
ring ttm
they can do them all
A
akki
Guest
[quote author=Scruff link=topic=3319.msg32923#msg32923 date=1187603386]
You already have both of them fitted to your car. The wastegate is fitted to the turbo and the dump valve is fitted to your intercooler.
Alan
[/quote]
Yep, thats not 100% right Alan but very close
The Waste Gate diverts exhaust gases away from the turbine wheel in a turbocharger when the boost pressure limit is reached to avoid over boost. This causes the turbine to lose speed, which in turn reduces the rotating speed of the compressor. The primary function of the wastegate is to stabilize boost pressure in turbocharger systems, to protect the engine and the turbocharger. The wastegate is controlled by a wastegate actuator in which the actuator is controlled by pressure coming from the intake manifold. So far so good...
The Dump Valve sit between the turbo outlet and the throttle body. When transitioning from a boosted state to a closed throttle state (as in between shifts), due to inertia, the turbo continues to pressurize air, but the closed throttle prevents the compressed air from entering the engine. In this case the pressure exceeds the preset spring pressure in the dump valve and the excess pressure is bled off to atmosphere.
Even with a dump valve the compressed air acts as a brake on the turbo (slowing it down), because the pressure on the backside of the turbo is at a higher pressure than on the front side (and the air actually wants to flow through the turbo backwards).
A blowoff valve (BOV, sometimes hooter valve, dump valve) is a more elegant solution to this problem by allowing the turbo to "freewheel" when the throttle is closed (equalizing the pressure on both sides of the turbo). Unlike a dump valve a blowoff valve can be used at multiple boost settings without reconfiguration.
Blowoff valves are sometimes incorrectly called dump valves because they serve a similar function, but they are very different solutions to the same problem.
I hope I don't bore you with my technical mumbo-jumbo The Subaru usually has a compressor bypass valve (CBV) also known as a compressor relief valve which is a vacuum-actuated valve designed to release pressure in the intake system when the throttle is lifted or closed. This air pressure is re-circulated back into the non-pressurized end of the intake (before the turbo) but after the mass airflow sensor. Thats why you hear nothing or just slight whisteling noises when the original CBV is in place
I have a Baileys Blowoff Valve and it sounds great I would go for it.
Axel
You already have both of them fitted to your car. The wastegate is fitted to the turbo and the dump valve is fitted to your intercooler.
Alan
[/quote]
Yep, thats not 100% right Alan but very close
The Waste Gate diverts exhaust gases away from the turbine wheel in a turbocharger when the boost pressure limit is reached to avoid over boost. This causes the turbine to lose speed, which in turn reduces the rotating speed of the compressor. The primary function of the wastegate is to stabilize boost pressure in turbocharger systems, to protect the engine and the turbocharger. The wastegate is controlled by a wastegate actuator in which the actuator is controlled by pressure coming from the intake manifold. So far so good...
The Dump Valve sit between the turbo outlet and the throttle body. When transitioning from a boosted state to a closed throttle state (as in between shifts), due to inertia, the turbo continues to pressurize air, but the closed throttle prevents the compressed air from entering the engine. In this case the pressure exceeds the preset spring pressure in the dump valve and the excess pressure is bled off to atmosphere.
Even with a dump valve the compressed air acts as a brake on the turbo (slowing it down), because the pressure on the backside of the turbo is at a higher pressure than on the front side (and the air actually wants to flow through the turbo backwards).
A blowoff valve (BOV, sometimes hooter valve, dump valve) is a more elegant solution to this problem by allowing the turbo to "freewheel" when the throttle is closed (equalizing the pressure on both sides of the turbo). Unlike a dump valve a blowoff valve can be used at multiple boost settings without reconfiguration.
Blowoff valves are sometimes incorrectly called dump valves because they serve a similar function, but they are very different solutions to the same problem.
I hope I don't bore you with my technical mumbo-jumbo
The Subaru usually has a compressor bypass valve (CBV) also known as a compressor relief valve which is a vacuum-actuated valve designed to release pressure in the intake system when the throttle is lifted or closed. This air pressure is re-circulated back into the non-pressurized end of the intake (before the turbo) but after the mass airflow sensor. Thats why you hear nothing or just slight whisteling noises when the original CBV is in placeI have a Baileys Blowoff Valve and it sounds great
I would go for it.Axel
jim dublin
Petrolheads
Would you have to get a blow off valve fitted before mapping
A
akki
Guest
[quote author=jim dublin link=topic=3319.msg33629#msg33629 date=1188070149]
Would you have to get a blow off valve fitted before mapping
[/quote]
That doesn't matter. The blow off valve doesn't influence the mapping in any way nor increases the boost.
You can re-map first or put in the valve first.
If you put in a manual boost controller you shuld be carefully and re-map first to match the new boost with the mapping.
Akki
Would you have to get a blow off valve fitted before mapping
[/quote]
That doesn't matter. The blow off valve doesn't influence the mapping in any way nor increases the boost.
You can re-map first or put in the valve first.
If you put in a manual boost controller you shuld be carefully and re-map first to match the new boost with the mapping.
Akki
keith dublin
Member Number 161Full ISDC Members 2015
Good man akki
A
akki
Guest
[quote author=keith dublin link=topic=3319.msg33633#msg33633 date=1188070609]
Good man akki
[/quote]
Thanks Keith
I try to become "Middle Lane Hog" and have to catch up with some more postings
Since I have had soooo much trouble with my boost settings, cut off's and all this stupid stuff, I have learned lots of things about turbos...
Akki
Good man akki
[/quote]
Thanks Keith
I try to become "Middle Lane Hog" and have to catch up with some more postings
Since I have had soooo much trouble with my boost settings, cut off's and all this stupid stuff, I have learned lots of things about turbos...
Akki
D
Dave571
Guest
Well explained Akki
Yeh very well explained.
The "fffffaffing" noise sometimes heard is known as compressor surge. This is when some of the air is recirculated back towards the turbo and the noise is made as the blades "cut" the air.
A lot of people like this noise but I would have though that it slows the turbo down and an atmospheric BOV would be a better choice as the ECU will read the MAF readings on the intake side of the MAF sensor anyway. With the recirculating BOV it dumps the air back into the air intake pre-MAF sensor so the MAF still reads airflow mass at the MAF sensor anyway (rather than on the on the side of the MAF).
There's a long running debate that atmospheric DV's are bad for the engine because the engine can run lean but as the MAF constantly takes readings on the intake side of the MAF sensor this shouldn't happen.
Of course this is only my laymans logic and I stand to be corrected and certainly there are members who know a whole lot more about this than me.
Frawls
The "fffffaffing" noise sometimes heard is known as compressor surge. This is when some of the air is recirculated back towards the turbo and the noise is made as the blades "cut" the air.
A lot of people like this noise but I would have though that it slows the turbo down and an atmospheric BOV would be a better choice as the ECU will read the MAF readings on the intake side of the MAF sensor anyway. With the recirculating BOV it dumps the air back into the air intake pre-MAF sensor so the MAF still reads airflow mass at the MAF sensor anyway (rather than on the on the side of the MAF).
There's a long running debate that atmospheric DV's are bad for the engine because the engine can run lean but as the MAF constantly takes readings on the intake side of the MAF sensor this shouldn't happen.
Of course this is only my laymans logic and I stand to be corrected and certainly there are members who know a whole lot more about this than me.
Frawls
A
akki
Guest
[quote author=FRAWLS link=topic=3319.msg34528#msg34528 date=1188577369]
[...]
Of course this is only my laymans logic and I stand to be corrected and certainly there are members who know a whole lot more about this than me.
Frawls
[/quote]
Hi Frawls,
nono... you are very well informed and thats how I understand it as well.
On a car where the blowoff valve is mounted after the mass airflow sensor, venting to atmosphere cnould confuses the engine control unit (ECU) of the car. The ECU is told it has a specific amount of air in the intake system, and injects fuel accordingly. The amount of air released by the blowoff valve is not taken into consideration and the engine runs rich for a period of time. Thats the reason, why you hear this rumble noise from turbo cars when they just release the throttle pedal. Failfires during gear shift are also a reason caused by too rich fuel injection.
Engines with a manifold absolute pressure regulated ECU or where the blowoff is mounted upstream of the MAF sensor are not affected.
And that is whe we have on the Subaru. Since our ECU has a boost pressure sensor, we are not affected by the Blowoff valve.
Too rich fuel injection has another down side. Eventually this can foul spark plugs and destroy the catalytic converter (when running rich, not all the fuel is burned which can heat up on and melt the converter or leave heavy carbon deposits).
But the guys from Subaru had already thought about that
Akki
[...]
Of course this is only my laymans logic and I stand to be corrected and certainly there are members who know a whole lot more about this than me.
Frawls
[/quote]
Hi Frawls,
nono... you are very well informed and thats how I understand it as well.
On a car where the blowoff valve is mounted after the mass airflow sensor, venting to atmosphere cnould confuses the engine control unit (ECU) of the car. The ECU is told it has a specific amount of air in the intake system, and injects fuel accordingly. The amount of air released by the blowoff valve is not taken into consideration and the engine runs rich for a period of time. Thats the reason, why you hear this rumble noise from turbo cars when they just release the throttle pedal. Failfires during gear shift are also a reason caused by too rich fuel injection.
Engines with a manifold absolute pressure regulated ECU or where the blowoff is mounted upstream of the MAF sensor are not affected.
And that is whe we have on the Subaru. Since our ECU has a boost pressure sensor, we are not affected by the Blowoff valve.
Too rich fuel injection has another down side. Eventually this can foul spark plugs and destroy the catalytic converter (when running rich, not all the fuel is burned which can heat up on and melt the converter or leave heavy carbon deposits).
But the guys from Subaru had already thought about that
Akki